Adding on the postage for the UK on the ebay link above I actually paid a couple of quid more at the Nissan dealership, but, there is not just one blank, you have to get the right blank for your car. The one I have is for a R33 GTR (BCNR33) and the Nissan Part number is KEY00-00185.
There is at least two different blanks (the difference is in the shoulders and the length of the actual key seemingly). The Nissan dealership let me watch as they entered my chassis number into their system for the correct blank as their first general search threw up two different blank part numbers.
They also did a "practice" cut on a Micra blank (same as the BCNR33) to make sure they could copy the original key correctly as they did not want to waste the "real" one. This did not cost me anything, in fact they did not charge me at all for the cutting.